I think the simplest explanation is the right one here. Thee was an affair and Paula got a little jealous because of the unpaid social liaison Jill Kelley was to close to her squeeze and she send threatening letters. She never figured she would then go to the FBI but she did and the FBI properly concluded that so far national security was not at stake so far so what do they have but an affair. Not earth shattering. However the FBI agent feeling scorned and thinking like most right wing conspiracy nuts runs off to Eric Cantor who calls the FBI head and now the cats out of the bag.
Thankfully I fired my biographer before this all broke and my wife has not asked me any questions.